The present invention relates generally to ground stations for communicating with and controlling satellites, and more particularly to a shared ground station for communicating with and controlling multiple independently launched and operated satellites simultaneously.
Ever since the launch of Sputnik in 1957 and the resulting ground swell of science education that resulted, satellites and satellite technology have played a major role in the advancement of space and communication technology. All manner of communication signals ranging from telephone, microwave, television and others can be transmitted over satellite communication links. In addition, a wide range of scientific and technical data can be gathered from specially designed satellite equipment to monitor weather and other physical phenomenon.
There are two primary types of orbits that are used for communication satellites. The first is a geostationary (GEO) orbit. A satellite placed into a geostationary orbit completes one revolution around the Earth in exactly the same amount of time that it takes the Earth to complete one revolution on its axis. Although the satellite is rapidly moving traveling around the Earth, the satellite appears to observers on the ground to be fixed in space above the Earth. A satellite in GEO orbit is approximately 22,300 miles above the Earth. Even at the speed of light, the period of time required to send and receive a radio signal over that distance (which is known as xe2x80x9clatencyxe2x80x9d) is about 0.24 seconds, which is unacceptable long for anything approaching real-time transmission. In addition, the relatively long distance requires higher power transmitters, and bigger antennas, which means more weight and greater costs to produce and launch a satellite into GEO orbit.
However, there are other advantages to a GEO orbit. From the relatively long distance from Earth, a much larger area falls within the reach of the satellite transmitter. Thus, a small number of satellites in GEO orbit can be used to provide coverage over all of the Earth""s surface. Conversely, a large number of satellites are required to provide similar coverage for just the opposite reason, i.e., the satellite transmitter falls on a much smaller surface area of the Earth.
In order to solve the latency problem, which is critical to achieving a commercially successful communication system, satellites can be placed into Low Earth Orbit (LEO), which is typically 500-1500 miles from Earth. At this much shorter distance, the satellites orbit the Earth about once every ninety minutes. At LEO distance, the latency is on the order of hundredths of a second. With the satellites located about an order of magnitude closer to the Earth, the transmitter can be much smaller and lower powered. However, the surface area on the Earth that is in range of a transmitter of a satellite in LEO is much smaller than if the satellite were in a GEO orbit. Therefore, many more satellites need to be launched into orbit in order to provide sufficient surface area coverage, although the launch costs for a LEO satellite are usually lower.
When satellites first were used, almost all satellites were manufactured and launched by national governments. At that time, the cost was far too high for commercial ventures, particularly in light of the small benefits and the high risks. In the beginning, the infrastructure did not exist to take advantage of the communication capabilities of satellites. Television was in its infancy and the enormous need to telecommunication that exists today had not even begun to develop.
However, as integrated circuit technology advanced, microprocessors became more powerful and memory prices plummeted, the cost to produce cellular phones, microwave transmitters, and other communications devices has radically decreased. This decrease in prices has led to an enormous increase in the telecommunications market. All telephone area codes, assigned under an earlier set of rules, have been allocated and a new area code assignment scheme had to be implemented to accommodate the rapid growth and the increase in phone numbers needed due to increased use of modems, facsimile machines, pagers, and of course, telephones.
Now, that the telecommunications market is of sufficient size, commercial entities can profitably operate satellite systems. A number of commercial companies have implemented their own satellite communication programs. As discussed earlier, the LEO orbits, which require smaller and less expensive satellites would require the launching of hundreds of commercially owned private satellites.
There are four major costs involved in a satellite communication network. These are manufacturing the satellite, launching the satellite, equipment and overhead to communicate with the satellite and general administrative overhead.
Initially, communication equipment requirements were met by companies building and maintaining their own ground-based communications stations. For a LEO, depending on the type of orbit and the altitude of the satellite, the satellite will be in communication with a single fixed ground station for only a few minutes during each rotation of the Earth. For example, for a typical LEO satellite orbiting the Earth in a polar orbit, a ground station located at the equator only has access to the satellite for about four minutes a day. If there was a need to communicate with the satellite for a longer period of time, then the company would have to either place more satellites in orbit or build more ground stations, to achieve communications for a longer period of time. This might require up to 6-8 ground stations at a cost of over $2.5 million per ground station. This figure represents a major cost of initiating a satellite based communication system, and hence a major impediment to the entry of smaller players into the satellite communications market.
It is known to receive data from multiple satellites using a common ground station. For example, U.S. Pat. No. 5,603,077 discloses a satellite system and method for remote control of a satellite signal receiver. However, the system and method disclosed therein operates with geostationary satellites under the control of the same operator. Furthermore, this system and method does not provide the ability to transmit to any arbitrary satellite.
U.S. Pat. No. 5,579,367 also discloses a system in which reception of signals from multiple satellites is controlled by a network controller. This system also cannot provide two-way communication with arbitrary LEO and GEO satellites.
In sum, simply providing communications reception is not sufficient to enable a satellite owner to manage and control the satellite owner""s satellite. Each satellite requires its own unique setup in a ground station, both for transmission and reception. Furthermore, each satellite must be tracked independently of other satellites, and each satellite must be controlled potentially several times a day (or at least a month). Moreover, the operators of each satellite do not necessarily communicate with each other to resolve conflicts and establish communication standards, which are required to use existing ground stations.
The present invention is therefore directed to the problem of developing a ground station system for communicating with any arbitrary satellite, which can be shared among a number of users, including those of LEO and GEO satellites, thus eliminating the great expense of building and maintaining a private satellite communication system.
The present invention is also directed to providing a graphical user interface for each user to enable each user to directly communicate with a scheduling computer, and to transfer user data to the scheduling computer, which scheduling computer coordinates user data from a number of users, resolves conflicts, and uploads the data transferred to the ground stations to the proper orbiting satellite.
Furthermore, the present invention is also directed to providing a communication network by which an owner of the satellite can remotely communicate with the scheduling computer of the service provider to submit commands to be transmitted to the satellite, and to receive data streams returned from the satellite, which data can either be stored in the scheduling computer and passed onto the user at a later time or forwarded to the user in real time.
The present invention solves these and other problem by providing a remotely controlled ground station that can be operated and controlled from a central controller. Furthermore, the present invention provides that each user creates and stores a ground station configuration file at the central controller, which file contains the data necessary to configure the remotely controlled ground station to communicate with the user""s satellite. Thus, when the user desires to communicate with the user""s satellite, the user schedules a communication session with the central controller, which downloads the configuration file to the appropriate ground station. The appropriate ground station is determined based on current orbital characteristics of the satellite in question. A server at the ground station then uses the data in the configuration file to configure the equipment at the ground station to communicate with the desired satellite.
The present invention relates to a method for sharing a single system of ground stations between any number of arbitrary satellite owners, thus permitting the owners to transfer command information to their satellite, and collect data streams that are sent back from the satellite all via a standardized global communications system.
The present invention includes a graphical user interface that allows the user to prepare data to be communicated to a satellite at the user""s usual place of business. Usually, the data comprises a set of commands to be sent to a particular satellite which will cause a desired and expected response from the satellite. The data is then transmitted to a central controller. The data can be prepared ahead of time and transmitted at one time to the central controller, or the user can communicate online directly with the central controller and input the data directly to the central controller. In addition, the user can communicate with the central controller via an Internet browser, which communicates with a web page on a web server associated with the central controller. By one of the above described methods or any other way in which data can reasonably be transmitted to the central controller, a set of dataxe2x80x94which includes such information as the target satellite, from which ground station should the data be transmitted, which pass of the target satellite should be utilized and whether data should be anticipated to be received during this pass from the satellitexe2x80x94is now stored at the central controller.
The central controller then transmits this data to one of the plurality of remotely controlled ground stations best suited to communicate with the specified satellite at the specified time.
One exemplary embodiment of the graphical user interface includes a computer, such as a desktop computer, and associated software.
One exemplary embodiment of the central controller includes a computer, such as an engineering workstation, and associated software.
An exemplary embodiment of the remotely controlled ground station includes an RF transmitter, and RF receiver, and a transmission controller.
The present invention also includes a method of communicating with a plurality of users, which includes the steps of acquiring data from the plurality of users, and transmitting that data to a central controller, which stores the data. The method also includes the steps of identifying and resolving transmission, equipment communication link, and other scheduling conflicts, and then transferring the data to be transmitted to the appropriate ground station on an as needed basis. The ground station transmits to the appropriate satellite, which is selected based upon the schedule established by the central controller, the data acquired from the user. If there is data downloaded from the satellite during the same pass, that data is temporarily stored by the ground station and then transferred to the central controller for forwarding to the particular user.
One exemplary embodiment for communicating between the user and the central controller and the remotely controlled ground stations, is by using a web browser communicating over an Internet connection to a web server that is programmed to store and display information about the satellites. This method of implementing communication between the user and the central controller is very effective because of universal access to the Internet. There are a large number of independent Internet service providers that make access to the Internet very simple and easily accomplished just about anywhere in the world.
It is important to differentiate the use of the Internet as a physical communication apparatus and the user of a web browser, which interprets and implements Hyper Text Markup Language (HML) files. Though use of a web browser is currently the most popular way to communicate over the Internet, there will certainly be major growth and changes in the software used to communicate over the Internet. At some point people may no longer be using a web browser and its underlying HTML files, but may communicate using some completely different software protocol. Thus, one aspect of the present invention relates to communication over a global network which utilizes a server computer that stores and implements a program written in a special communication language. The end user operates a client version of that same software to enable the end user to interact with the client computer receiving the files of the special communication language. Those files are then interpreted by the client software to enable the user to view and read the resulting presentation of text and graphics, input data, and transmit that data to the server computer via the Internet network.